Severe Thunderstorm Warning 143, NWS Pittsburgh, PA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1030 AM EDT MON JUL 18 2011

.SYNOPSIS...
A WEAK COLD FRONT, MOVING SOUTHWARD FROM THE GREAT LAKES, CAN GENERATE
SCATTERED THUNDERSTORMS THIS AFTERNOON AND TONIGHT. THIS FRONT
WILL RETREAT NORTHWARD TUESDAY, AND SO HOT AND HUMID CONDITIONS
CAN BE EXPECTED THE REST OF THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
PER RECENT SATELLITE DATA, STRATUS WILL HAVE BURNED OFF BY 11 AM.
HIGH CLOUDS AND DEVELOPING CUMULUS ARE EXPECTED TO ONLY PARTIALLY
LIMIT SUNSHINE THE REST OF TODAY.

PER RECENT WRF-NMM AND SREF MODEL OUTPUT, EXPECT PREFRONTAL
SCATTERED THUNDERSTORMS TO DEVELOP SOUTHWARD OF THE GREAT LAKES
THIS AFTERNOON AND EARLY TONIGHT, WHEN STORMS CAN BECOME MORE NUMEROUS.

DUE TO HUMID SURFACE LAYER, THUNDERSTORMS CAN BE POWERED BY GREAT
INSTABILITY. SURFACE FRONT AND SHORT-WAVE TROUGH ALOFT IN
NORTHWEST FLOW WILL ORGANIZE THUNDERSTORM DEVELOPMENT ALSO,
PERHAPS INTO SHORT-LINES. SO CONCUR WITH SPC REGARDING SLIGHT RISK
OF SEVERE. WILL ALSO MONITOR FOR HEAVY RAINFALL.

MADE SMALL ADJUSTMENTS TO FORECASTED TEMPERATURES BASED ON RECENT
HRRR AND NAM AND SREF MODEL OUTPUT. SURFACE DEW POINTS IN THE
UPPER 60S WILL UP APPARENT TEMPERATURES/HEAT INDEX VALUES/ INTO
THE 90S.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
FORECAST OF PRECIP PROBABILITIES WAS TAPERED DOWNWARD LATER
TONIGHT AND THROUGH TUESDAY DUE TO EXPECTED SOUTHWARD PROGRESS OF
THE WEAK FRONT. GIVEN PROGGED BUILDING OF HIGH PRESSURE ON
WEDNESDAY, HAVE ONLY FORECAST SLIGHT PRECIP NUMBERS WITH DIURNAL
RESTRICTIONS IN THE RISING HEAT.

HOT AND HUMID CONDITIONS WILL THUS PREVAIL WITH HEAT INDEX
READINGS FORECAST IN THE UPPER 90S FOR AREAS SOUTHWEST OF
PITTSBURGH ON WEDNESDAY AFTERNOON. MENTION OF THE HOT AND HUMID
CONDITIONS WILL BE MAINTAINED IN THE HAZARDOUS WEATHER OUTLOOK.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
HOT, HUMID WEATHER WILL PERSIST INTO LATE WEEK AS STRONG UPPER
RIDGE OVER THE MIDWEST IS PROJECTED TO SLIDE EASTWARD. WITH AMPLE
LOW LEVEL MOISTURE IN PLACE, WILL KEEP AT LEAST A SLIGHT CHANCE
OF DIURNAL THUNDERSTORMS IN THE FORECAST FOR EACH DAY THOUGH
FRIDAY. A BETTER CHANCE OF PRECIPITATION EXISTS OVER THE WEEKEND
AS A FRONTAL BOUNDARY PUSHES INTO THE GREAT LAKES.

&&

.AVIATION /14Z MONDAY THROUGH FRIDAY/...
PER RECENT SURFACE AND SATELLITE DATA, EXPECT CONTINUED
IMPROVEMENT IN FLIGHT CONDITIONS TO MVFR ABOUT 15Z AND VFR 16Z-17Z
AS STRATUS CLOUDS LIFT AND FOG DISSIPATES, AND VFR CUMULUS
DEVELOPS.

A COLD FRONT WILL PUSH SOUTHWARD TOWARD THE REGION LATE THIS
AFTERNOON INTO THE EVENING HOURS. THIS FEATURE WILL PROVIDE A
FOCUS FOR SCATTERED THUNDERSTORMS AND THE POTENTIAL FOR
RESTRICTIONS. WITH MESOSCALE MODELS INCREASING CONFIDENCE, TEMPO
GROUPS FOR TSRA WITH MVFR RESTRICTIONS WERE INCLUDED IN TAFS FOR
THIS EVENING EVERYWHERE EXCEPT KMGW. IT IS POSSIBLE THAT A FEW OF
STORMS MAY BE SEVERE WITH A THREAT OF GUSTY WINDS. THE CHANCE OF
SHOWERS AND STORMS WILL CONTINUE THROUGH MOST OF THE OVERNIGHT
PERIOD WITH A WARM AND HUMID AIR MASS IN PLACE.

OUTLOOK /TUESDAY THROUGH FRIDAY/...
MVFR RESTRICTIONS IN HAZE WILL BE POSSIBLE AT TIMES TUESDAY THROUGH
FRIDAY AS A HOT AND HUMID AIR MASS BUILDS INTO THE REGION.
RESTRICTIONS ARE ALSO POSSIBLE IN PATCHY EARLY MORNING FOG AND
WIDELY SCATTERED AFTERNOON AND EVENING THUNDERSTORMS.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PITTSBURGH PA
414 AM EDT MON JUL 18 2011

MDZ001-OHZ039>041-048>050-057>059-068-069-PAZ007>009-013>016-020>023-
029-031-073>076-WVZ001>004-012-021>023-041-190815-
GARRETT-TUSCARAWAS-CARROLL-COLUMBIANA-COSHOCTON-HARRISON-
JEFFERSON OH-MUSKINGUM-GUERNSEY-BELMONT-NOBLE-MONROE-MERCER-VENANGO-
FOREST-LAWRENCE-BUTLER-CLARION-JEFFERSON PA-BEAVER-ALLEGHENY-
ARMSTRONG-INDIANA-WASHINGTON-GREENE-WESTMORELAND-WESTMORELAND RIDGES-
FAYETTE-FAYETTE RIDGES-HANCOCK-BROOKE-OHIO-MARSHALL-WETZEL-MARION-
MONONGALIA-PRESTON-TUCKER-
414 AM EDT MON JUL 18 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN MARYLAND...EAST
CENTRAL OHIO...NORTHWEST PENNSYLVANIA...SOUTHWEST
PENNSYLVANIA...WEST CENTRAL PENNSYLVANIA...NORTHERN WEST VIRGINIA
AND NORTHERN PANHANDLE OF WEST VIRGINIA.

.DAY ONE...TODAY AND TONIGHT.

THERE IS A CHANCE FOR SEVERE THUNDERSTORMS TODAY WITH THE PRIMARY
THREATS COMING FROM DAMAGING WIND AND LARGE HAIL.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.

STRONG HIGH PRESSURE IS PROJECTED TO BUILD ACROSS THE REGION
DURING THE LATTER HALF OF THE WEEK. IF THIS OCCURS...THE HOTTEST
TEMPERATURES THUS FAR THIS SUMMER WILL BE LIKELY WITH HEAT INDEX
VALUES WELL INTO THE 90S TO NEAR 100 IN SOME AREAS.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

15

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PITTSBURGH PA
1215 PM EDT MON JUL 18 2011

PAZ007>009-181715-
FOREST PA-MERCER PA-VENANGO PA-
1215 PM EDT MON JUL 18 2011

...STRONG THUNDERSTORMS WILL AFFECT NORTHERN FOREST...NORTHERN MERCER
AND NORTHERN VENANGO COUNTIES...

AT 1208 PM EDT...STRONG THUNDERSTORMS WERE ALONG A LINE FROM 18 MILES
NORTH OF PLEASANTVILLE TO 7 MILES WEST OF CONNEAUT LAKE...MOVING
SOUTHEAST AT 25 MPH.

WIND GUSTS TO 50 MPH AND HAIL UP TO DIME SIZE ARE POSSIBLE WITH THESE
STORMS. THERE CAN ALSO BE LOCALLY HEAVY RAIN AND A SHORT INTERVAL OF
FREQUENT LIGHTNING.

SOME LOCATIONS THAT WILL BE IMPACTED INCLUDE...
  GREENVILLE...         MAURICE K GODDARD STATE PARK...
  PLEASANTVILLE...      WEST HICKORY...
  OIL CREEK STATE PARK...                     LYNCH...
  COOPERSTOWN...        BALLTOWN...

WHEN THUNDERSTORMS THREATEN...GO INDOORS IF YOU CAN.

DO NOT DRIVE YOUR VEHICLE INTO AREAS WHERE THE WATER COVERS THE
ROADWAY. THE WATER DEPTH MAY BE TOO GREAT TO ALLOW YOUR CAR TO CROSS
SAFELY. MOVE TO HIGHER GROUND. CAMPERS...WATCH STREAM LEVELS AND BE
READY TO MOVE TO HIGHER GROUND.

PLEASE REPORT SIGNIFICANT WEATHER TO THE NATIONAL WEATHER SERVICE BY
CALLING TOLL FREE...877-633-6772...WHEN YOU CAN DO SO SAFELY.

LAT...LON 4162 7895 4159 7897 4140 8000 4139 8051
      4142 8053 4149 8052 4149 8001 4163 7983